Many countries in the world are considering a return to nuclear power as an alternative to energy production from dwindling supplies of fossil fuels. However, the public has considerable concerns over the health implications of a nuclear power plant accident such as the one at occurred at the Chernobyl Nuclear Power Plant on April 26th 1986. This project seeks to provide a high quality resource (the Chernobyl Tissue Bank: CTB) of biospecimens from those who were affected most by the Chernobyl accident and to make these available to scientists worldwide. Material from the resource has already been used in a number of projects worldwide and the result from these projects has already changed the way in which the molecular biology of radiation associated thyroid cancer is interpreted. This a prospective study that collects material from patients who were born on or after 26th April 1967 i.e. those who were born prior to the accident and exposed to various radionuclides in utero, childhood or adolescence who were exposed to both short-lived isotopes (e.g. 131-I) and longer lived isotopes (e.g. 137-Cs), and those who were born subsequent to the accident and therefore exposed only to low level longer lived isotopes in the environment (e.g. 137-Cs). The latter provide a very valuable control population, resident in the same areas and of the same racial background, but exposed to a longer term consequence of the accident. The project builds on relationships with physicians and scientists in Ukraine and Russia that have been established since 1992 and provides a platform for long-term monitoring of the radiobiological health consequences of the accident. Full informed consent is obtained from participants in the project and biosamples are anonymised prior to release to scientific projects. Research results from tine scientific projects that use the resource are returned to the project on a case-by-case basis enabling correlation of results from different projects and the creation of a resource forfeiture bioinformatic studies. The studies that this project supports provide a wealth of information that can be used to define factors that confer increased risk for the development of thyroid cancer following a nuclear accident e.g. genetic predisposition, age at exposure and exposed dose, as well as seeking to understand the basic biology of thyroid cancer following radiation exposure and therefore more effective methods for monitoring and treatment.